The basic aim of this research proposal is to gather information on the electronic effects of substituents on the structure and metabolism of benzo(a)pyrene (BP), particularly in regard to the way in which reaction pathways are changed by the substituents. These studies may indicate whether multiple pathways of activation are possible for substituted BP's and if they are likely to occur for BP itself. Such information could lead to a better understanding of the mechanisms of carcinogenesis and mutagenesis which may be useful indesigning methods to alleviate the effects of exposure to such carcinogens. In this proposal the specific effects of alkyl or fluoro substitution will be considered. The electronic effects of substituents will be investigated by analysing the electron paramagnetic resonance (EPR) spectra of the cation radicals of all twelve mono-methylated BP's and 6-, 7-, 8-, 9-, and 10-mono-fluoro-BP's. Several strategies will be employed to analyse these spectra including selective deuteration and alternate methods of radical production. The EPR spectra of the 6-oxy radicals produced by chemical and enzymatic oxidation will also be investigated to obtain information on the effects of substituents on this pathway of metabolism. From these studies the coefficients of the highest occupied molecular orbital of BP will be evaluated and changes in these coefficients brought about by substitution may reflect on the products of enzymatic metabolism. Additionally, the possibility of an alternate pathway of activation for methyl substituted BP's, involving the formation of an hydroxymethyl derivative, will be investigated.